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Laboratory Manual ELEN-325 Electronics

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Laboratory Manual ELEN-325 Electronics Laboratory Manual ELEN-325 Electronics Department of Electrical & Computer Engineering Texas A&M University Prepared by: Dr. Jose Silva-Martinez ([email protected]) Rida Assaad ([email protected]) Raghavendra Kulkarni ([email protected]) - 1 - Contents Experiment 1 - Network Analysis and Bode plots 3 Experiment 2 - Introduction to NI Elvis Environment 7 Experiment 3 - Operational Amplifiers-Part I 18 Experiment 4 - Operational Amplifiers-Part II 25 Experiment 5 - Operational Amplifiers-Part III 29 Experiment 6 - Introduction to Diodes 37 Experiment 7 - Characterization of the BJT 43 Experiment 8 - BJT Amplifiers: Basic configurations 48 Experiment 9 - BJT amplifiers: Design project 54 Experiment 10 - Characterization of the MOS transistor 56 Experiment 11 - CMOS amplifier configurations 60 Experiment 12 - CMOS amplifiers: Design project 64 Appendix A – OPAMP Datasheets Appendix B – Diode Datasheets Appendix C – BJT Datasheets Appendix D – MOSFET Datasheets Acknowledgments This manual was inspired from the previous ELEN-325 laboratory manual thanks to the effort of many people. The suggestions and corrections of Prof. Aydin Karsilayan, Felix Fernandez, Mandar Kulkarni in College Station and Wesam Mansour, Haitham Abu-Rub, Khalid Qaraqe in TAMU, Qatar are recognized. We would like to thank TAMU Qatar for the financial support while this lab manual is being constantly updated. We are thankful to National Instruments for generous donations of several NI Elvis Workstations. Copyright Texas A&M University. All rights reserved. No part of this manual may be reproduced, in any form or by any means, without permission in writing from Texas A&M University. - 2 - Lab 1: Network Analysis and Bode plots Objectives: The purpose of the lab is to investigate the frequency response of a passive filter and get the fundamentals on circuit design and analysis in the frequency domain. List of Equipment required: a. Protoboard b. Capacitors c. Resistors d. Oscilloscope e. Function generator f. Frequency counter g. Digital Multimeter Introduction Frequency domain representation The frequency response is a representation of the system’s response to sinusoidal inputs at varying frequencies; it is defined as the magnitude ratio and phase difference between the input and output signals. If the frequency of the source in a circuit is used as a reference, it is possible to have a complete analysis in either the frequency domain or the time domain. Frequency domain analysis is easier than time domain analysis because differential equations used in time transforms are mapped into complex but linear equations that are function of the frequency variable s (σ+j). It is important to obtain the frequency response of a circuit because we can predict its response to any other input. Therefore it allows us to understand a circuit’s response to more complex inputs. Filters are important blocks in communication and instrumentation systems. They are frequency selective circuits and widely used in applications such as radio receivers, power supply circuits, noise reduction systems and so on. There are four general types of filters depending on the frequency domain behavior of the transfer function magnitude; Low-pass filters (LPF) that pass low frequency signals and reject high frequency components; Band- pass filter (BPF) pass signals with frequencies between lower and upper limits; High-pass filter (HPF) pass high frequency signals and rejects low frequency components; and finally, Band-Reject (Stop) filters that reject signals with frequencies between a lower and upper limits. In this laboratory experiment we will plot the frequency response of a network by analyzing RC passive filters (no active devices are used such as opamps or transistors). We can characterize the filter by two features of the frequency response: 1. What is the difference between the magnitude of the output and input signals (given by the amplitude ratio) and 2. What is the time lag or lead between input and output signals (given by the phase shift) To plot the frequency response, a number of frequencies are used and the value of the transfer function at these frequencies is computed. A particularly important method of displaying frequency response data is the Bode plot. According to your lecture notes, a Bode plot is the representation of the magnitude and phase of H(s) if H(s) is the transfer function of a system and s =σ+ j where is the frequency variable in rad/s. Phase measurement A method to measure the phase angle by determining the time shift t, is to display the input and output sine waves on the two channels of the oscilloscope simultaneously and calculating the phase difference as follows, - 3 - Fig. 1. One way of measuring phase angle. t Phase difference (in degrees) = 360 T where t is the time-shift of the zero crossing of the two signals, and T is the signal’s time period. Pre-laboratory exercise 1. For the circuit shown in Fig. 2, derive the transfer function for vo/vin in terms of R, and C, and find the expressions for the magnitude and phase responses. Express your results in the form v 1 o v s in 1 p where ωp is the pole frequency location in radians/second. R Vin(t) C Vo(t) Fig. 2. First order lowpass filter (integrator) 2. The corner frequency of the lowpass filter is defined as the frequency at which the magnitude of the gain is 1 2 0.707 of the DC gain (ω = 0). This is also called the half power frequency (since 0.7072 =0.5), and the -3dB frequency since 20log10(0.707) = -3dB. Find, in terms of R and C, the frequency in both Hz and in rad/s at which the voltage gain is 0.707 of the DC gain (ω = 0). 3. For C = 47nF, find R so that the –3dB frequency is 3.3kHz. Draw the bode (magnitude and phase) plots. 4. Simulate the low pass filter circuit using the PSpice simulator. Compare the simulation results with your hand-calculation. Attach the magnitude and phase simulation results, and compare them to your bode plots from step 3. 5. For the circuit shown in Fig. 3, derive the transfer function for vo/vin in terms of Ri , and Ci, and find the expressions for the magnitude and phase responses. You may assume R2 >> 2R1 . Express your results in the form - 4 - v 1 o vin s s 1 1 p1 p2 where ωp1 and ωp2 are the pole frequency locations (in radians/second) in terms of Ri and C. 6. Design (find component values) a passive second-order low pass filter such as the one shown in Fig. 3. Determine R1 and R2 for C = 47nF such that the first pole is at 1,700 Hz and the second pole is at 35 Hz. You must use PSpice to verify your design. 7. Draw the bode plots, and compare them to the magnitude and phase simulation results using PSpice. R1 R2 Vin(t) C C Vo(t) Fig. 3. Second order low pass filter Lab Measurement: Part A. First order low pass filter 1. Build the circuit shown in Fig. 2 with the values of R and C you choose in the pre lab. Apply a 6Vpp sinusoidal signal from the function generator to the input, using the high Z option on your signal source (ask you TA for assistance). 2. Connect channel 1 of the oscilloscope across vin(t), and channel 2 across vo(t). Set the oscilloscope to display both inputs vs. time by pressing CH1 and CH2. Keep the generator voltage constant. Vary the input frequency and find the –3dB frequency (first determine the low frequency, DC, gain and then sweep the frequency until the output is 3dB below the input. Then take a few measurements around this frequency to find the exact one). Your data should include several points above and below the –3dB frequency, if possible within a couple of decades around that frequency. 3. Use the cursors on the oscilloscope to measure the time shift, t, between the zero crossings of the input and output signals for at least 10 different frequencies in the range 0.1f-3dB and 10f-3dB, including f-3dB, and get the phase shifts between input and output signals. Measurement of the phase shift is an accurate method of determining the –3dB frequency. What is the phase shift at f-3dB? Part B. Noise Filtering 1. Noise filtering is studied in this part. Noise is modeled as a high frequency, small amplitude signal and superimposed onto an ideal sine wave. A low pass filter can attenuate the high frequency noise while preserving the wanted signal. 2. Evoke the ArbWave software; 3. Generate a sine wave. Select a sine wave using the Waveforms icon; 4. Add noise to signal. Select the edit icon and use the select all utility, then select the math icon, choose the add utility. In the add function box, select the standard wave option. Next select the noise waveform and adjust it to 0.3V. In the add function box, choose the fit amplitude option; 5. Send the noisy waveform to the signal generator. Use I/O icon and select send waveform. Adjust the amplitude of the signal to 6Vpp, and the frequency to 0.25kHz; 6. Apply this signal to your lowpass filter and observe the input and output signals; 7. Take a screen shot of both the noisy and filtered signals on the oscilloscope. - 5 - Part C. Second order low pass filter 1. Build the circuit shown in Fig. 3 with R and C you found in the pre lab. Apply a 6Vpp sinusoid from the function generator to the input. 2. Find the -3dB signal-attenuation frequency f-3dB and 40dB signal-attenuation frequency f-40dB.
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